Is this powdery mildew?

[BalconyBonsai]

Hi, I have noticed that my trident maple have a white powder-like substance around the edges of many of it's leaves. I'm trying to understand what it is and if I need to deal with it. The closest I have found is powdery mildew but from looking at pictures online it still doesn't look very similar. The powder on my tree pretty much only sticks to the edges of the leaves and doesn't form any spots. If I rub it with my finger nail it is removed. There is some similar stuff at the base of the trunk and it is most visible when not wet. The tree is not sheltered to the wind and is facing south with no protection against the sun.

Appart from this the tree seems healthy to me and new shoots are popping up all over the tree and it looks normal I think. I have seen similar stuff on my deshojo that sits just beside it but on that it very sparse.

Do you think I need to do anything about this? I think leaves will drop in at most a couple of months but I don't want something to hibernate and then "attack" the tree just as it wakes up.

 

[John P.]

Now is the time of year for all of us in the Northern hemisphere to have mildew issues. I just noticed some on a couple of my small valley oaks, and hit them with some copper yesterday evening.

Probably worth hitting them with something just to be sure. Even a hydrogen peroxide mixture if you don’t have labeled sprays on hand.

 

[Bnana]

In the northern hemisphere we get more mildew now but I would not call it issues. It's rarely a problem and definetly not in your case.
This is normal and happens with trees in the wild as well, it's a result of leaves getting old and higher humidity. It's no reason to start spraying nasty stuff on your trees.
New leaves in spring will be fine.

 

[Clorgan]

I'm getting a bit of this at the moment too, weather is all over the place here. Had also read that it's not harmful, but I'm new so I'm not the person to advise!

 

[John P.]

In the northern hemisphere we get more mildew now but I would not call it issues. It's rarely a problem and definetly not in your case.
This is normal and happens with trees in the wild as well, it's a result of leaves getting old and higher humidity. It's no reason to start spraying nasty stuff on your trees.
New leaves in spring will be fine.

When the leaves get covered with powdery mildew they won’t photosynthesize. And it typically attacks newer leaves first.

Trees in the wild suffer all sorts of problems. Would you let your bonsai trees get eaten by caterpillars, too?

 

[Bnana]

If it's early in the season and badly affected I would agree, in this case it hardly harms the tree.
If it is bad you should improve conditions for the tree, not spray toxic metals.
A caterpillar is easy to remove but if a few leaves are eaten on a healthy tree it's not a big deal.

 

[BalconyBonsai]

Now is the time of year for all of us in the Northern hemisphere to have mildew issues. I just noticed some on a couple of my small valley oaks, and hit them with some copper yesterday evening.

Probably worth hitting them with something just to be sure. Even a hydrogen peroxide mixture if you don’t have labeled sprays on hand.

Ok, good to hear I'm not alone at least. What do you mean by copper? Some anti-fungicide containing copper? Is that safe for the trees?

 

[BonsaiDTLA]

Ok, good to hear I'm not alone at least. What do you mean by copper? Some anti-fungicide containing copper? Is that safe for the trees?

Copper fungicide is commonly used to treat powdery mildew. Not sure if Amazon is in Sweden, but there's a link attached for you to check out.

It's safe for your trees so long as you follow the manufacturer's instructions. But don't over do it and be extra sure not to get it on your skin/eyes, etc.

 

[Firstflush]

Did you check under the leaves to see if there is anything fuzzy underneath? If there is, it’s white fly.

Regarding powdery mildew, you can also mix baking soda with water and spray. Changing the PH of the leaf surface will stop the mildew too. Research to find the appropriate mix, but typically....1 tablespoon per gallon.

....and always test spray first on a small area away from the viewing front to make sure the tree is not adversely affected.
Spray in the evening out of direct sun.

 

[Wires_Guy_wires]

1.5% peroxide will deal with most mildew. However, since the mildew has been chewing away at the cuticle, it's going to leave some brownish stains when it's gone.
It's a matter of preference.
I don't treat it at all because either I don't get mildew issues, or I get them just before leaf drop.

 

[Bnana]

Copper fungicide is commonly used to treat powdery mildew.

In the US it might be but in many countries the use is strongly regulated as it is toxic and the copper accumulates in the soil or ends up in groundwater. I wouldn't be amazed if it's illegal to use as fungicide in Sweden.

 

[BalconyBonsai]

In the US it might be but in many countries the use is strongly regulated as it is toxic and the copper accumulates in the soil or ends up in groundwater. I wouldn't be amazed if it's illegal to use as fungicide in Sweden.

If so, what would be the alternative? I found some recipe using baking soda but that was only for preventative purposes.

 

[sorce]

If everything else is fine, and you are certain of what you have, then consider spraying.

This is not advice to save the planet, it's to keep the variables down.

You Don't have powdery mildew.

You do have a nice tree with ugly caked around the trunk.
Odd how it looks like it would cause this slight damage.

Rather than look to what isn't. Look to what IS!

If I had a tree that nice, I'd keep that trunk clean.

Reckon that clear up your problem.

Sorce

 

[BalconyBonsai]

If everything else is fine, and you are certain of what you have, then consider spraying.

This is not advice to save the planet, it's to keep the variables down.

You Don't have powdery mildew.

You do have a nice tree with ugly caked around the trunk.
Odd how it looks like it would cause this slight damage.

Rather than look to what isn't. Look to what IS!

If I had a tree that nice, I'd keep that trunk clean.

Reckon that clear up your problem.

Sorce

I'm not sure what you mean by "caked" but you are probably correct that I should clean it.

How would you suggest I'd do it? Should the soil at the trunk be level with the rest of the soil? I always just assumed it was planted like that.

 

[Bnana]

What kind of water do you use? Is it hard?
On the trunk it looks like calcium deposits. Using rainwater would solve that.

I wouldn't expect calcium deposits on the leaves like this.

 

[sorce]

I'm not sure what you mean by "caked" but you are probably correct that I should clean it.

How would you suggest I'd do it? Should the soil at the trunk be level with the rest of the soil? I always just assumed it was planted like that.

Something is off with the planting, which cleaning will likely uncover. Those seem to have been an intended root layer that failed, or an accidental layer that showed up with moss that was too high, or too wet maybe.

It's an odd situation, so your remedy will be equally odd.

If you uncover something resembling a good beginning of a single radial layer, you may have to build a "fence" around the outside rim to allow heightening the soil level.

Maybe you will dig further and remove soil.

I don't remember, this is the way you received this tree correct? You haven't repotted it to know what the roots are doing?

Sorce

 

[BalconyBonsai]

Something is off with the planting, which cleaning will likely uncover. Those seem to have been an intended root layer that failed, or an accidental layer that showed up with moss that was too high, or too wet maybe.

It's an odd situation, so your remedy will be equally odd.

If you uncover something resembling a good beginning of a single radial layer, you may have to build a "fence" around the outside rim to allow heightening the soil level.

Maybe you will dig further and remove soil.

I don't remember, this is the way you received this tree correct? You haven't repotted it to know what the roots are doing?

Sorce

Sorry if I'm being stupid but, do you mean they made the mound to cover up extra roots that had grown higher up on the trunk? Don't I risk disturbing the roots by removing the soil? I will repot this in the spring so I'm not sure if it's worth messing with it before that.

What do you mean, build a fence?

The tree came like this from the store, I pretty much haven't done anything besides watering and pruning it. But there are issues with the soil where water hardly passes through it.

 

[sorce]

My guess is it was pulled from either a grow pot, or the ground, and rather haphazardly put into a bonsai pot to sell.

Can't say this is "wrong", it gives us something to do, which is what our happy newb scissor fingers want anyway right!?

If you look at @Shibui recent content, perhaps he could share a picture, you can see what a ground grown specimen looks like, and how this "mound" of questionable roots becomes.

Trouble with this one, is it seems it has been wet around that moss too long, as of a decision wasn't made soon enough. Which makes for a little more delicate work on your end.

The tree seems healthy enough to not do too much worrying, and allow some study. By the time you're ready to Repot you'll have it figured out.

Oh, tweezers and a toothpick or 2, that's how I'd clean it. Gently, get to know it, take your time.

Sorce

 

[leatherback]

If so, what would be the alternative?

Milk in water and spray.

 

[Shibui]

What kind of water do you use? Is it hard?
On the trunk it looks like calcium deposits. Using rainwater would solve that.

I wouldn't expect calcium deposits on the leaves like this.

I agree that this looks far more like calcium deposit than mildew. The ring of white around the edges is typical. I have seen similar deposits when the trees are regularly misted or lightly watered and evaporation is high.

As for @sorce concern with ugly roots: Everything depends on what you expect and like. It is not really clear what that base is. It could be a mossy buttress, widening of the trunk where it meets the roots. In that case it is entirely natural and probably good.
It could still be masses of smaller roots. Given a few years they will all fuse into a single, solid mass to give a wide buttressed trunk base.
In either case I don't see any problem.